Sitting on a mine

Africa’s groundwater potential, from MacDonald et al. (2012)

As discussed last week, some of the most proliferating farmer-led irrigation techniques involve groundwater as a source for water abstraction, therefore I wanted to investigate Africa’s groundwater potential in this week’s post.


MacDonald et al. (2012) estimate that much of Africa is sitting on top of a goldmine – a goldmine consisting of around 0.66 million km3 of water.  To put this into perspective:

- Average annual in Africa is estimated to be 0.02 million km3,
- Total lake water storage is estimated to be 0.03 million km3,
- Total renewable freshwater resources are estimated to be 0.004 million km3,

Thus, the estimated volume of Africa’s groundwater is more than 12 times a great as its annual rainfall, lake water storage and renewable freshwater resources combined.  In addition to this, Damkjaer and Taylor (2017) explain that common water scarcity metrics, such as the water stress index (WSI), withdrawal-to-availability (WTA), and even more holistic metrics that try to capture elements of a country’s adaptive capacity, such as the social water stress index (SWSI), all fail to account for available groundwater as they use mean annual river runoff as a measure of freshwater availability, thus excluding groundwater potential.  Perhaps this is why Africa’s future relating to issues of water scarcity and food insecurity are often portrayed so bleakly?  

However, whilst Africa sits atop all of this unaccounted groundwater, Altlchenko and Villhoth (2015) highlight that only between 692-1644km3 year-1 exists as renewable groundwater for irrigation.  Moreover, Giodarno (2006) explains that the spatiality of this renewable groundwater is severely limited, with over half renewable groundwater supplying only 4/54 countries across the continent, namely Nigeria (in eastern West Africa) Cameroon, Congo and the Democratic Republic of Congo (in western Central Africa).  Nonetheless, the utilisation of groundwater, both renewable and non-renewable, to supply water for irrigation have been advocated for as a means of sustaining water supply despite interannual fluctuation in rainfall, in order to increasing food security where applicable.  As I covered renewable groundwater systems in Nigeria and Malawi last week, I will focus on non-renewable groundwater systems for the remainder of this post. 

The Nubian Sandstone Aquifer System: A Fossil Aquifer 

As you can see from the map of Africa’s groundwater storage, much of it is located – rather bizarrely – in the hyper-arid northeast of the continent, underneath the Sahara Desert.  According to Bakhbakhi (2006), this aquifer is shared by Chad, Egypt, Libya and Sudan and spans over 2.2 million km2.  He explains that as a result of growing demand compared to freshwater availability in this hyper-arid region, largely for irrigation, over 40 billion km3 has already been abstracted, from this non-renewable aquifer, by Libya and Egypt only, resulting in a 60m decline of its maximum water level.  Such a decline can increase the cost of abstraction as deeper wells are needed to extract water, usually at a higher cost.  In addition to this, Pallas and Margat (2004) explain that abstraction can lead to a modification in the direction of flow of the groundwater; if ‘upstream’ groundwater abstraction, it reduces the flow of water ‘downstream’, which is problematic if one nation is upstream and the other is downstream.  Not only this, but abstraction can lead to saltwater intrusion in coastal areas, making the groundwater saline, and therefore disallowing its use for irrigation.  Since the abstraction of groundwater can be plagued with negative impacts, hindering its future use for irrigation, cooperation between the users of transboundary aquifers is necessary, which has manifest as the ‘law of transboundary aquifers’.  The law states that: 

“Each aquifer State has sovereignty over the portion of a transboundary aquifer or aquifer system located within its territory. It shall exercise its sovereignty in accordance with international law...”, and that: “Aquifer States shall utilize transboundary aquifers or aquifer systems according to the principle of equitable and reasonable utilization,”.

Final Thoughts

This post has exposed how Africa is a groundwater-rich continent, although its spatial distribution is highly variable across the continent. Nonetheless, many of the ‘water-scarce’ nations of Africa could be reclassified if groundwater was included into popular water scarce indexes. This highlights the potential for the expansion of groundwater extraction for irrigation to achieve food security - and thus SDGs 2 and 6.  However, as exemplified in the Nubian Sandstone Aquifer, groundwater extraction must be treated with caution and involve the cooperation between transboundary states in order to achieve equitable utilisation without unintended externalities.  In the next post I will be discussing another method used to achieve water and food security, applicable in Africa

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